Tunable power amplifier matching circuit

ABSTRACT

A power amplifier matching circuit is provided. The matching circuit includes a ferro-electric tunable component. A control signal is applied to the tunable component, changing the component&#39;s impedance. This changes the impedance of the matching circuit.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application60/283,093, filed Apr. 11, 2001, which is hereby incorporated byreference. In addition, this application relates to U.S. applicationSer. No. 09/904,631 filed on Jul. 13, 2001, Ser. No. 09/912,753 filed onJul. 24, 2001, Ser. No. 09/927,732 filed on Aug. 8, 2001, Ser. No.09/927,136 filed on Aug. 10, 2001, “Tunable Capacitor,” filed on Jan.11, 2002, and “Antenna Interface Unit,” filed on Feb. 8, 2002, which arehereby incorporated by reference.

BACKGROUND

Wireless communication devices, such as, but not limited to, wirelesstelephones, use many electronic components to transmit and receivesignals over the air. A transceiver is the part of a wireless telephonethat actually sends and receives signals. The front end of a transceiveris the portion of a transceiver closest to the air interface in thesignal path. The front end includes an antenna and several componentsnear the antenna in the signal path. Several of the components requiredin the front end of the transceiver are power amplifiers (PA's),isolators, low noise amplifiers (LNA's) and multiplexers. Each of thesecomponents are typically manufactured as packaged devices. In the caseof a PA or an LNA, this package typically includes the active device andinternal input and output matching circuits for bringing the input andoutput resistances up to an industry standard 50 ohms.

In one common embodiment, the packaged PA is comprised of a highperformance FET (e.g., GaAs) placed on a ceramic or other substrate.Other active devices can be used, such as, for example, bipolar junctiontransistors (BJT's) and high electron mobility transistors (HEMT's). Thematching circuits may be patterned on the ceramic substrate, or they maybe fabricated using lumped surface mount technology (SMT) components.The FET is bonded to the package substrate, possibly to a metal heatsink, then typically connected to its input, output and bias pads usingbond wires.

Depending on the requirements, multi-stage PA devices may be used aswell. This means that one PA device may include more than one amplifyingtransistor. This may be necessary for a number of reasons. One possiblereason is to produce the required gain. In the case of a multi-stage PAdevice, inter-stage impedance matching circuits may be used as well, tomatch between the output of one stage and the input of the followingstage.

The inputs, outputs and bias lines to the FET are routed down to theceramic substrate. After passing through the matching circuits, theinput and output lines are routed off of the substrate down to theunderlying printed wire board (made of FR-4 in most cases) throughconnectors on the PA package. Further wire bonding may be required toconnect the package pads to the input, output and bias lines.

The package further comprises some kind of packaging (typically polymer)encasing, in whole or in part, the FET and the ceramic substrate holdingthe matching circuits. The input and output bias leads can be found atthe edge of the packaging.

Isolators, duplexers, diplexers and low noise amplifiers (LNA's) arehandled in much the same way. As packaged devices, they each have theirseparate substrates with their separate matching circuits bringing theirinput and output impedances to 50 ohms.

Most RF test equipment can only test parts at an impedance of about 50ohms. Manufacturers and designers typically want to be able to test eachpart separately. Historically, the only way this could be done was ifeach part had input and output impedances of around 50 ohms. For thisreason, parts, such as PA's and LNA's, for example, have typically beenmanufactured with impedances equal to about 50 ohms. This has requiredthe use of extensive input and output matching circuits for many ofthese parts.

A duplexer is one of the primary components in a transceiver front end.The duplexer has three ports (a port is an input or an output). One portis coupled to an antenna. A second port is coupled to the transmitsignal path of the transceiver. The duplexer couples the transmit pathto the antenna, so that the transmit signal can be transmitted on theantenna.

A third port is coupled to the receive path of the transceiver. Theantenna coupled the antenna to the receive path, so that the receivedsignal can be received by the receive path of the transceiver.

An important function of the duplexer is to isolate the transmit signalfrom the receive path of the transceiver. The transmit signal istypically much stronger than the receive signal. Some of the transmitsignal inherently gets down the receive path. But this transmit signalgoing down the receive path must be greatly reduced (or attenuated).Otherwise, the transmit signal going down the receive path will swamp,or overwhelm, the receive signal. Then the wireless telephone will notbe able to identify and decode the receive signal for the user.

The required attenuation of the transmit signal going down the receivepath is achieved at some expense. The duplexer also attenuates thetransmit signal going to the antenna for transmission. This attenuationin the transmit signal going to the antenna is known as loss. It wouldbe beneficial to reduce the transmit path loss in the duplexer.

Additionally, the duplexer typically must be large accomplish thereceive path attenuation of the transmit signal. Consumers arecontinually demanding smaller and smaller wireless telephones with moreand more features and better performance. Thus, it would be beneficialto reduce the size of the duplexer while maintaining or improving thetransmit signal attenuation in the receive path and simultaneouslymaintaining or improving the transmit signal loss to the antenna.

SUMMARY

Transceivers account for a significant portion of the cost, size andpower consumption of wireless communication devices. The front end,including antennas, duplexers, diplexers, isolators, PA's, LNA's andtheir matching circuits accounts for a significant portion of the cost,size and power consumption of the transceiver. It would be beneficial toreduce the cost, size and power consumption of these parts, individuallyand together.

Briefly, the present invention provides a ferro-electric tunableduplexer integrated with one or more of the other parts. Thiscombination is referred to herein as an antenna interface unit. Morespecifically, in addition to adding F-E tunability, the presentinvention integrates one or more of the above components on onesubstrate. The components are integrated on one substrate either byplacing each component, with the appropriate matching circuit directlyon the substrate, or by direct fabrication of the component and matchingcircuit into or onto the substrate.

For example, in the case of integrating the PA, the isolator and theduplexer, the PA active device (e.g., GaAs FET) is placed directly ontothe common substrate. As part of the integration of components, thematching circuits for the components may be patterned or placed on thecommon substrate. The matching circuits for the PA would be patterned orplaced on this substrate. The isolator, if used, could be fabricateddirectly on this common substrate or mounted as a discrete component.

The matching circuit between the isolator and the duplexer would bepatterned or fabricated on the substrate. The isolator would have itsjunction patterned on this substrate, with the ferrite puck, magnet andshield placed over it.

For purposes of integration, a stripline duplexer may be preferred as itwould use the common substrate as one half of each resonator.Additionally, its length is shorter than a corresponding microstriprealization. Whatever type of duplexer is used, any coupling and tuningcapacitors would be patterned on the common substrate. It will beunderstood that the same kind of integration can be carried out for theLNA, diplexer and antenna matching circuits. If minimum loss is a keyrequirement for a post PA BPF, duplexer or multiplexer, then a low losssubstrate must be used as is well known to those skilled in the art.

The topology of the matching circuits would be typical matching circuittopologies with two key exceptions: (1) they would be integrated withthe other parts and matching circuits on the common substrate and (2)they may comprise F-E tunable components, though they need not allcomprise F-E tunable components. The PA and isolator matching circuitswould typically be pi matching circuits (shunt capacitor, seriesinductor or microstrip line, shunt capacitor). The isolator typicallyuses series or shunt reactive circuits. The diplexer and duplexermatching circuits would typically be simply series input and outputcapacitors. The antenna matching circuit would be a pi or T circuit withL-C ladders creating a higher order matching circuit. Preferably, theduplexer would be as claimed in U.S. patent application Ser. No.09/912,753 filed on Jul. 24, 2001.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a side view of an antenna interface unit.

FIG. 2 is a schematic diagram of a power amplifier matching circuit.

FIG. 3 is a schematic diagram of an extended power amplifier matchingcircuit.

FIG. 4A is a schematic diagram of a multiband power amplifier matchingcircuit.

FIG. 4B is a schematic diagram of another multiband power amplifiermatching circuit.

FIG. 5 is a schematic diagram of an isolator and its three matchingcircuits.

FIG. 6 is a schematic diagram of a LNA matching circuit.

FIG. 6B is a graph of a LNA noise figure response.

FIG. 7 is a schematic diagram of an antenna matching circuit.

FIG. 8 is a block diagram of an antenna interface unit.

FIG. 9 is a block diagram of an antenna interface unit.

FIG. 10 is a block diagram of an antenna interface unit.

FIG. 11 is a block diagram of an antenna interface unit.

FIG. 12 is a block diagram of an antenna interface unit.

FIG. 13 is a block diagram of an antenna interface unit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to FIG. 1, an integrated antenna interface unit (AIU) 12is shown. While a duplexer is shown, as is common in a CDMA handset, amultiplexer could be used as well. While the description that followsspecifies a duplexer throughout, it is to be understood that amultiplexer or BPF could be substituted for the duplexer. A PA unit 20,an isolator unit 24, and a duplexer 28 are all attached to a commonsubstrate 16, eliminating the need for individual substrates for each ofthese components.

The substrate is preferably made of a carefully selected material. Thesubstrate parameters that are typically critical are dielectricconstant, loss tangent, thermal properties, cost and ease of processing.Typically, a dielectric constant should be less than about 40, and theloss tangent should be less than about 0.001 in the frequency range ofinterest. A low loss substrate may be more expensive than a higher losssubstrate. A designer must frequently balance the issues of cost andperformance parameters such as loss. Additionally, metal loss must alsobe minimized. A substrate must be chosen that can accommodate a low lossmetal.

Advantages of integration of components with a multiplexer include: (1)reduction of the overall loss associated with the integrated devicecompared to that arising from using discrete parts, thus making iteasier to meet specifications; (2) reduction of the footprint of the Txchain in the sybsystem; (3) reduction of the overall parts count,especially as far as a manufacturer of a wireless communication deviceis concerned; (4) reduction of cost due to reduced packaging and partscount, (5) integration of f-e tunable components with lower added lossand occupying less space than if introduced as individual, lumpedelement components.

A PA-to-isolator matching circuit 41, disposed on the substrate 16,couples the PA unit to the isolator unit 24. An isolator-to-duplexermatching circuit 44, disposed on the substrate 16, couples the isolatorto the duplexer.

Preferably, an isolator is used, but it is optional. If no isolator isused, it will be understood that the isolator is removed and thePA-to-isolator matching circuit and the isolator-to-duplexer matchingcircuit is replaced by a PA-to-duplexer matching circuit. There are twomain reasons a designer will choose to use an isolator in a design suchas disclosed herein. The reasons are: (1) To provide a certain loadimpedance to the device preceding the isolator (the PA in this case);and (2) To prevent unwanted signals from propagating back into thedevice preceding the isolator (the PA in this case). Unwanted signalspropagating back to the PA can cause unacceptable mixing or distortionor both to be created which can render the overall design unacceptable.

As is well known in the art, there are many cases where the isolator canbe eliminated. This is true when: (1) The PA can be presented anacceptable load under operating conditions; or (2) The isolator can bereplaced by a suitable coupler or passive hybrid device that reduces theeffect of reverse power propagation on the desired signal path. Passivecouplers or passive hybrid couplers can be more easily implemented bydirect fabrication on the substrate as outlined in this application.

This particular configuration of the AIU 12 is shown and described indetail for purposes of example and illustration only. The AIU 12 may notinclude a PA 20 or an isolator 24. As will be described more generallywith reference to FIGS. 8-13, the AIU always has a tunable multiplexerand some other component on a common substrate. Other than that, thereare many possible components that can be integrated with the multiplexerto form the AIU. The PA and isolator are just two examples.

Also, the PA may include multiple active devices. This is called amulti-stage PA. The discussion will be in terms of one active device,but it will be understood by those skilled in the art that thisdiscussion could be applied to multi-stage PA's.

Since the matching circuits and components are on a common substrate 16,the impedance matches do not have to be to the industry standard 50ohms. Instead, the impedance match can be from the natural outputimpedance, Z_(o), of one component to the natural input impedance,Z_(i), of the next component.

For example, referring again to FIG. 1, if the PA unit 20 has an outputimpedance of about 2.5 ohms and the isolator unit 24 has an inputimpedance of about 12.5 ohms, the PA-to-isolator matching circuit 41will match the impedance from 2.5 ohms at the PA unit 20 to 12.5 ohms atthe isolator unit 24. This is in contrast to the prior art. In the priorart, the PA unit would typically have its own substrate, and theisolator unit would typically have its own substrate. The PA unit wouldhave its own matching circuit which would match from the output of thePA (e.g., 2.5 ohms) up to 50 ohms. The isolator unit would have its ownmatching circuit which would match from 50 ohms down to the isolator(e.g., 12.5 ohms). There would be additional loss in the signal in thismatch up to 50 ohms from 2.5 ohms and back down to 12.5 ohms from 50ohms.

A further advantage in matching from the natural ouput impedance of onedevice to the natural input impedance of another device is that asimpler topology in the matching network may often be used when Zo andZi are closer in value than they are to the industry standard 50 ohms,for example. A simpler matching network will result in less addedvariation due to component variation than does a more complex network.In the limit where, for example, Zo=Zi, no matching network is neededbetween adjacent devices in the signal path. In the prior art, eachdevice is typically matched to the industry standard 50 ohms.

Referring again to FIG. 1, the duplexer 28 is a low loss tunableduplexer, as described in U.S. patent application Ser. No. 09/912,753filed on Jul. 24, 2001. Ferro-electric components such as ferro-electriccapacitors are used to tune the duplexer.

The integrated antenna interface unit has significantly less loss in thetransmit path than non-integrated transmit chains. Integratingcomponents, the PA, for example, eliminates lossy attachments, which aredescribed in U.S patent application Ser. No. 09/912,753 filed on Jul.24, 2001. Specifically, an electrical connection between the PAsubstrate and the common substrate is eliminated. In the prior art, thePA is typically manufactured on its own substrate. When a communicationdevice is made, incorporating the PA, an electrical connection must bemade between the PA substrate and the common substrate. Whether this isaccomplished by surface mount technology (SMT), hand soldering, wirebonding, or some other attachment method, attachment losses are added.By mounting the PA directly on the common substrate, these losses areavoided.

Referring now to FIG. 2, a PA matching circuit 48 is shown. A PA 50 hasan input 52 and an output 54. In a preferred embodiment, the output 54is coupled to a first capacitor 56. The first capacitor 56 is alsocoupled to ground. The output 54 is also coupled to an inductive element58. The inductive element 58 may be a lumped element inductor, amicrostrip line, or any other inductive element known in the art. Theinductive element 58 is also coupled to a second capacitor 60. Thejunction between the inductive element 58 and the second capacitor 60forms the output 65 of the PA matching circuit 48. The output 54 of thePA 50 is also coupled to a bias circuit. The bias circuit typicallycomprises an inductor 68, a third capacitor 71 and a voltage source 74.

Another example matching circuit topology is shown in FIG. 3. Thematching circuit 72 is similar to the matching circuit 48 shown in FIG.2, except that the matching circuit 72 in FIG. 3 has an additionalinductive element 74 and an additional capacitor 76. Also, the output 78of this matching circuit 72 is at the junction of the inductive element74 and the capacitor 76. Any or all of the inductive and capacitivecomponents may be tunable.

It will be understood by those of skill in the art that differentmatching circuit topologies might be used to implement the PA matchingcircuit. In general a more complex matching circuit will allow forgreater control in the match at the expense of added insertion loss(I.L.) due to finite component Q, as well as greater cost and increasedboard space.

Referring again to FIG. 1, the PA is placed directly on the substrate16, and the matching circuit described with reference to FIG. 2 isfabricated directly on the substrate 16. The capacitors may befabricated directly on the substrate 16 as interdigital capacitors, gapcapacitors or overlay capacitors, as is well known in the art. Byfabricating the PA unit 20, the PA-to-isolator matching circuit 41 andthe isolator unit 24 directly on the same substrate 16, attachmentlosses are avoided, in addition to the previously described lossesresulting from matching impedances up to and back down from 50 ohms. Inthe prior art, the separate substrates for the PA unit and the isolatorunit must be attached electrically and mechanically to a commonsubstrate or board. There are losses associated with attachment of theseadditional substrates. Finally, there is additional loss in theelectrical line connecting the separate substrates on the commonsubstrate or board. By combining the PA and isolator onto a commonsubstrate these losses are eliminated or significantly reduced.

Referring again to FIG. 2, the capacitors 56 and 60 may be tunable,using low loss tunable ferro-electric materials and methods as describedin U.S. patent application Ser. No. 09/912,753 filed on Jul. 24, 2001,and Ser. No. 09/927,136 filed on Aug. 10, 2001, hereby incorporated byreference. This would reduce the loss even further, by providing for anoptimum impedance match. The matching circuits shown in FIGS. 2 and 3are used to match a single band, such as the PCS band, or the cellularband. Presently, these matching circuits can achieve a tunability of atleast 15%.

This allows for tuning even over several international PCS bands, suchas from the India PCS band to the U.S. PCS band. To tune over a widerfrequency, for example, from the U.S. PCS band at about 1900 MHz to theU.S. cellular band at about 800 MHz, the PA-to-isolator matching circuithas to have more tunability.

For tuning a PA over more than one PCS band, the input matching circuitmay need tuning as well. Whether tuning the input matching circuit isnecessary or not can be determined on a case by case basis. The sametechnique as used for the output matching circuit is used in this case.

Increased tunability is attained by adding micro-electro-mechanicalswitches (MEMS) to the matching circuit. Referring now to FIG. 4A, amultiband PA matching circuit 31 is shown. The matching circuit 31 issimilar to that of FIG. 2, except that several additional componentshave been added, with the ability to switch those components in and outof the circuit 31 with MEMS. The output 35 of a PA 33 is coupled, as inFIG. 2, to a first capacitor 37 and to a first inductive element 39. Thefirst inductive element 39 is coupled to a second capacitor 43. Buthere, the output 35 of the PA 33 is also coupled to a first MEMS 45 forselectively coupling to a third capacitor 47. The first inductiveelement 39 and the second capacitor 43 are also coupled to a second MEMS80 for selectively coupling to a fourth capacitor 83. These switches 45and 80 and capacitors 47 and 83 change the capacitance of the matchingcircuit 31.

Additionally, the first inductive element 39 is coupled at either end toMEMS 86 and 89 for selectively coupling to a second inductive element92. These switches 86 and 89 and inductive element 92 change theinductance of the matching circuit 31. In this way, the matching circuit31 can be used to match the PA 33 for use at either cellular or PCSbands. It will be understood that the techniques and devices describedhere could be used to match at other bands than the cellular and PCSbands. The cellular and PCS bands are chosen as examples. It will alsobe understood that other matching circuit topologies can be chosen.

Referring again to FIG. 4A, a multi band PA matching circuit 31 is shownwhich is similar to the single band PA matching circuit described withreference to FIG. 2. As stated the multi band PA matching circuit 93 hasan advantage in that it is tunable over a broader range of frequencies,due to the addition of MEMS switches 86, 89, 45 and 80 and accompanyingcomponents. Tunable capacitors 37 and 43 and tunable reactive element 39can be used to fine tune over a specific frequency band. The specificband is selected by MEMS switches 86, 89, 45, and 80.

In addition to MEMS switches 86, 89, 45, and 80, the multi band PAmatching circuit 93 has additional capacitors 47 and 83 and anadditional reactive element 92. Capacitor 83 is connected in series withcapacitor 43 and in series with MEMS switch 80. When it is desired toswitch to another band, such as, for example, another PCS band, MEMSswitch 80 is activated, coupling capacitor 83 to capacitor 43 andreactive element 39 for changing the impedance of matching circuit 93.Similarly, MEMS switch 45 can be activated to couple capacitor 47 tocapacitor 37 and reactive element 39 for changing the impedance ofmatching circuit 93. Also similarly, MEMS switches 86 and 89 can beactivated to couple reactive element 92 in parallel to reactivecomponent 39 for changing the impedance of matching circuit 93.

An alternative configuration of reactive components 92 and 39 and MEMSswitches 86 and 89 is shown in FIG. 4B. In FIG. 4B MEMS switches 86 and89 are coupled to reactive elements 92 and 39 such that only one ofreactive elements 92 and 39 is coupled to capacitors 37 and 43. Reactiveelement 39 can be switched out of the circuit, so that it isdisconnected at both ends, whereas, in FIG. 4A, reactive element 39 isalways coupled to the circuit at capacitors 37 and 43. Reactive element92 only is switched in and out of the circuit. Note that in both FIGS.4A and 4B any of the elements 92, 39, 47, 37, 83 and 43 may be tunable.At least one is tunable, but as few as one, or all of them, may betunable.

For handset applications, the MEMS switches described here should havethe lowest practical loss, e.g., DC resistance less than about 0.01ohms. Switching speed is not critical so long as it is less than about1.0 ms. Clearly, other applications may require other criticalspecifications on the MEMS switches.

Referring now to FIG. 5, an isolator matching circuit will now bedescribed. An input port 97 is coupled to a PA (not shown), to a firstimpedance element 99 and to a second impedance element 101. The firstand second impedance elements 99 and 101 form an input matching circuitfor the isolator 95. The second impedance element 101 is coupled toground, and the first impedance element 99 is couple to the isolator 95for transmitting a signal from a PA (not shown) to the isolator 95. Boththe first and second impedance elements may be ferro-electric tunablecomponents, as described in U.S. patent application Ser. No. 09/927,136filed on Aug. 10, 2001.

An output of the isolator 95 is coupled to a third impedance element103, which is coupled to a fourth impedance element 105. The third andfourth impedance elements 103 and 105 together form an output matchingcircuit and an output port 107 for the isolator 95. The output port 107is coupled to a duplexer (not shown). Both the third and fourthimpedance elements may be ferro-electric tunable components, asdescribed in U.S. patent application Ser. No. 09/927,136 filed on Aug.10, 2001.

An isolation port 104, is coupled to an impedance element 109. Theimpedance element 109 is coupled to another impedance element 115 and toa resistor 118. Together the impedance elements 109 and 115 and theresistor 118 comprise an isolation matching circuit.

It will be understood by one of skill in the art that the input, outputand isolation matching circuits described with reference to FIG. 5 using“L” matching sections are illustrative only. Other topologies for thesematching circuits could be used, such as, for example, parellel LCcircuits, “T”, or Pi networks, as described in U.S. patent applicationSer. No. 09/927,136 filed on Aug. 10, 2001.

Advantageously, each of the impedance elements 99, 101, 103, 105, 109,and 115 are preferably formed directly on the common substrate describedwith reference to FIG. 1. This reduces losses associated with attachingseparate units to the substrate, reduces cost and eliminates the need tomatch components up to the 50 ohm industry standard.

Regarding the PA, its characteristic output impedance for CDMA handsetsis typically about 2-4 ohms near the maximum output power level requiredof it. The isolator characteristic impedance is typically about 8-12ohms. Filters can be designed with input and output impedances that cantake on a broad range of values. Since duplexers and diplexers are madeprimarily of filters, they can be designed to allow for a broad range ofinput and output impedances. Thus, they can be designed to match towhatever impedance is convenient based on the rest of the circuit.

Referring now to FIG. 6A, a preferred LNA matching circuit 117 will nowbe described. An input port 118 is coupled to a first inductor 121 andto a capacitor 124. The capacitor is coupled to a second inductor 127.The second inductor 127 is coupled to a third inductor 130 and to an LNA133.

The matching circuits will be used to match the impedance between thevarious parts to avoid or reduce power loss in the signal travellingfrom one part to the other. For LNA applications, there is anotherpurpose. For LNA applications, impedance transforming networks orcircuits are used primarily to maintain an optimum noise impedance matchbetween the input signal source and the active device chosen for theLNA. In fix-tuned circuits, the optimum noise impedance match isobtained at one frequency and is dependent on both temperature andcomponent variations. In the tunable circuit approach described here,the optimum noise impedance match can be made adjustable to covermultiple bands or a wider frequency range than is possible in thefix-tuned case. An added advantage in using tunable components is theability to compensate for temperature variations.

The introduction of f-e or other tunable components allows for increasedflexability in the design of LNA's. In the conventional design usingfixed elements, one must usually trade-off optimum noise figure andmaximum gain. With tunable components, one can allow for cases where theinput matching circuit can be varied from the minimum noise figure andthe maximum gain, as desired.

A tunable optimum noise figure will now be described with reference toFIG. 6B. FIG. 6B is a graph showing noise figure 120 plotted againstfrequency 122. Typically, such as, for example, in a CDMA wirelesscommunication device, there will be a maximum noise figure 126 specifiedfor a given design of an LNA. The maximum noise figure specified isshown as a horizontal dashed line 126. A curve showing a typical noisefigure response 128 is shown as the solid curve.

Typically, the LNA and its matching circuits will be designed so thatthe noise figure response 128 will be below the maximum noise figure 126at an operating frequency, f_(o) 130. A tunable LNA matching circuitallows the LNA noise figure response 128 to be tuned over frequency. Thetuned noise figure response 132 and 134 is represented by two dashedcurves of a similar shape to that of the typical noise figure response128. By tuning the noise figure response at 132 and 134, the noisefigure response can be made to be below the maximum noise figure 126 atalternate operating frequencies f₁ 138 and f₂ 140. It will be understoodthat f₁ 138 and f₂ 140 are chosen as representative frequencies only.The noise figure response can be tuned over a broad range offrequencies. Additionally, it will be understood by one of skill in theart that MEMS switches can be added to the LNA matching circuit tofurther broaden the range of tunability of the noise figure response.

Referring now to FIG. 7, a preferred antenna matching circuit will nowbe described based on a CDMA handset. An antenna 136 is coupled to afirst inductor 139 and to a second inductor 142. The first inductor 139preferably has an inductance equal to about 8.2 nH. The second inductor142 preferably has an inductance equal to about 3.9 nH.

The second inductor 142 is coupled to a first capacitor 145 and a secondcapacitor 148. The first capacitor 145 preferably has a capacitanceequal to about 0.5 pF. The second capacitor 148 preferably has acapacitance equal to about 2.7 pF. It will be understood that othercomponent values and matching circuit topologies can be used.

One side of the second capacitor forms an input and output port 149 forthe antenna matching circuit for coupling to a duplexer (not shown),diplexer (not shown), multiplexer (not shown) or other type of filter(not shown).

The antenna matching circuit will typically be a pi or T circuit with anL-C ladder making it a higher order match. This gives more tolerance forimpedance variation. Typically, the antenna in a system will be matchedto 50 ohms. There may be, however, an ideal impedance for a givenantenna that is other than 50 ohms, though 50 ohms is common for testdevices.

For example, a commonly used antenna for wireless communication devicesmay have an input impedance of 30 ohms. As previously mentioned, the PAmay have an ouput impedance of about 2 ohms. The isolator may have anouput impedance of about 12.5 ohms. The diplexer and duplexer filterscan easily accommodate a wide range of impedances.

So the PA-to-isolator match is from about 2 ohms at the PA to about 12.5ohms at the isolator. The isolator-to-duplexer match is from about 12.5ohms to about 12.5 ohms. The duplexer is at about 12.5 ohms. So theduplexer-to-diplexer match is about 12.5 to about 12.5 ohms. Thediplexer and duplexer inputs and outputs are at about the sameimpedance, for example, about 12.5 ohms. The diplexer-to-antennamatching circuit may be a match from about 12.5 ohms at the diplexer toabout 30 ohms at the antenna. Each of these matching circuits, plus thediplexer and the duplexer may be f-e tunable.

At mentioned above with reference to FIG. 1, it will be understood thata common substrate may include many different combinations of the partsmentioned above. In one embodiment, as shown in FIG. 8, a commonsubstrate 152 includes a duplexer 154, an isolator 156, a PA 157 and therequisite matching circuits (not shown). In another embodiment, as shownin FIG. 9, a common substrate 160 includes an antenna matching circuit163, a diplexer 166 and a duplexer 169. In yet another embodiment, asshown in FIG. 10, a common substrate 172 includes an antenna matchingcircuit 175, a diplexer 178 and two duplexers 181 and 184. In stillanother embodiment, as shown in FIG. 11, a common substrate 186 includesan antenna matching circuit 188, a diplexer 190, two duplexers 192 and194, two isolators 194 and 196, two PA's 198 and 200 and two LNA's 202and 204. In another embodiment, as shown in FIG. 12 a common substrate206 includes everything mentioned above with reference to FIG. 11,except the antenna matching circuit 188. In another embodiment, as shownin FIG. 13 a common substrate includes everything mentioned above withreference to FIG. 10, except the antenna matching circuit 175.

The integration of a PA module, isolator and duplexer for a CDMA TXchain removes the requirement that each stand-alone device be matched at50 ohms at the input and output. By allowing for a more gradualimpedance match (from about 2 ohms to about 30 ohms in the examplegiven) one can reduce match-induced losses. Additionally, the f-etunable components are exposed to a lower rf voltage, for a given power.

The reduced rf voltage, for a given power, reduces non-lineardistortion, because f-e films are typically non-linear. Alternatively, af-e component can be subjected to increased power while maintaining anacceptable level of non-linear distortion. Thus, designing integratedcomponents that operate at lower input and output impedances allows forf-e components to be incorporated in applications where higher powerlevels are required than possible with f-e components matched to theindustry standard 50 ohms.

Fabrication on a common substrate further reduces losses that naturallyarise when the components involved are packaged and mounted individuallyon a printed wire board (pwb).

By reducing Tx chain losses the Tx chain specifications can more easilybe satisfied. This means that the specification for one or more of theparts involved can be relaxed. For example, the PA or other high valuepart specifications can be relaxed. A high value part is a part with oneor more of the following characteristics: high cost, high performance,high level of difficulty in meeting specifications such as gain, powerout, stability, ACPR, over temperature, and unit-to-unit repeatability.

Since the specifications on the PA, for example, can be relaxed, thereare many possible benefits. For example, the PA may be able to meetspecifications while consuming less power. This results in longer talktimes or longer standby times or both. In another example, since Txchain losses are reduced, a wireless handset manufacturer may be able tomeet specifications with a PA that has less stringent tolerances orrequirements. The handset manufacturer may be able to choose a cheaperPA, reducing the cost of wireless handsets. These benefits of reduced Txchain losses are given as examples only. It will be understood by thoseskilled in the art that other benefits will arise from reduced Tx chainlosses. It will further be understood that these benefits can beutilized to improve wireless communication devices in ways other thanthose mentioned here.

1. A tunable power amplifier comprising: a power amplifier; aferro-electric tunable component coupled to the power amplifier; a poweramplifier output matching circuit coupled to the power amplifier, havingan impedance and comprising the ferro-electric tunable component; acontrol line operably coupled to the ferro-electric component; a controlsource electrically coupled to the control line, the control sourceconfigured to transmit a control signal on the control line; wherein theferro-electric component, responsive to the control signal, adjusts theimpedance of the matching circuit; and wherein the matching circuitcomprises: a first tunable ferro-electric capacitor coupled at a firstend of the first capacitor to an output of the power amplifier and toground at a second end of the first capacitor; an inductive elementcoupled at a first end of the inductor to the first tunable capacitorand to the power amplifier, and; a second tunable ferro-electriccapacitor coupled, at a first end of the second capacitor to a secondend of the inductive element and to ground at a second end of the secondcapacitor; wherein, the ferro-electric component comprises one of theferro-electric tunable capacitors; a second inductive element coupled ata first end of the second inductive element to the second end of thefirst inductive element; and a third ferro-electric tunable capacitorcoupled at a first end of the third capacitor to a second end of thesecond inductive element and at a second end of the third capacitor toground.
 2. The tunable power amplifier of claim 1, wherein the secondinductive element comprises a lumped element inductor.
 3. The tunablepower amplifier of claim 1, wherein the second inductive elementcomprises a microstrip.